My belief is moms and dads should agree that they will both ask for 50/50 custody in the case of a divorce. My agreement is more of a set of vows. I have not written a legally binding contract, like a pre-nuptial, that governs the money in the case of the divorce. I have written an agreement that governs the promise between the two parents to share the love and parenting of their children in a balanced way for the rest of their lives.
My ex-wife screwed me in the divorce and she and the therapist that setup our 70/30 parenting plan knew it. They were not basing their plans on science, but on "what's best for the kids" mythology that has been perpetuated since my parents got a divorce 49 years ago.